Figures 5 and 6 and Figures 7 and 8 should be considered in pairs. 
Two modified meters were built for use in the modified frame of type 
shown in Figure 2. They have been designated on the curves as Meter 
No. 1 and Meter No. 2. Meter No. 1 was the narrow-vane meter. Meter 
No. 2 was built of the hub ends and spiders from the original meter and 
a new axle and wider-vane assembly. Both meters were rated for pivot 
ball bearings and jewel bearings. There is no difference, of any 
practical significance, in the calibration curvesfor the two types of 
bearings in the same meter. There is a difference in curves for Meter 
No. 1 and Meter No. 2, which fact serves only to emphasize that each 
meter of any design must receive a separate calibration. That there is 
no comparable difference in bearing types is significant, and seems to 
indicate that friction had been reduced to a practical minimum with use 
of the pivot ball bearings. The lower limit of operation for both meters 
is 0.12 of a foot per second. 
The original meter with the narrower vanes was almost buoyant in 
water. Adding width to them, of course, was done at a sacrifice of that 
buoyancy. It is believed that restoring the original vane size would not 
materially aid in obtaining operation at velocities lower than 0.12 of a 
foot per second. The vanes had been enlarged in an attempt to gain a 
higher turning moment, but it appears that the maximum usable area had 
been reached on the first meter. It should be recognized that the vane 
shape was decided upon through consideration of geometric factors alone, 
and that no propeller design theories or practices were employed. 
It is pointed out that no provision has been made for indicating the 
direction of flow on the recording, as was done with the Pegram meter. 
This was not necessary because the curve of velocity drawn by the recorder 
is roughly the sine curve, and comparison with the curve shown by a tidal 
stage recorder located nearby, readily sets the direction of flow. The 
pattern is repetitive, and changes in direction take place slowly over 
periods of 2 to 6 hours. Without the direetional feature it is possible 
to use insulators on all vanes to obtain a higher input count to the counter 
circuit. This is an advantage, particularly at low velocities. 
In summary, the Bureau of Reclamation has a current meter which 
satisfies its present requirements. Though some additional development 
work might produce an improved design which would operate at lower veloci- 
ties, it contemplates no further effort in that direction. 
